Techniques have been known for graft modifying polyolefins represented by polyethylene or polypropylene with unsaturated carboxylic acids (e.g., acrylic acid) or anhydrides thereof (e.g., maleic anhydride) to introduce thereinto polar groups, to thereby impart adhesion between different kinds of substrates such as metals, glass, polar high-molecular weight materials, and polyolefins, as described, for example, in Japanese Patent Publication Nos. 18392/62 and 32654/77.
It has also been known to impart adhesion by copolymerizing .alpha.-olefins such as ethylene with polar monomers such as glycidyl (meth)acrylate, as described, for example, in Japanese Patent Publication No. 27527/71 and Japanese Patent Application (OPI) No. 11388/73 (the term "OPI" as used herein means "unexamined published application").
Though these graft modified polyolefins or copolymers exhibit fairly good initial adhesion to metals or glass, they have a drawback that their adhesion is appreciably deteriorated in a short period of time in an atmosphere where water is present. For example, with respect to the adhesion to glass, in packaging water-containing liquid foods such as sake, soy sauce, vinegar, mayonnaise, and jam, good maintenance of water-resistant adhesion between glass containers and their metallic lids is demanded, but the above-described graft modified polyolefins or copolymers cannot meet such a demand.
Furthermore, adhesives which are used in the area of food packaging are often required to have adhesion to metals, polar high-molecular weight materials, or polyolefins in addition to the above-described maintenance of water-resistant adhesion.
On the other hand, in order to improve a marked reduction in adhesion to glass in an atmosphere where water is present, it has been known to graft modify an ethylene-vinyl acetate copolymer with an unsaturated organosilane (see the Processings of the 23rd Annual Meeting of the Adhesion Society of Japan, pp. 118, June 12, 1985). However, such an ethylene-vinyl acetate copolymer graft modified with an unsaturated organosilane does not have satisfactory adhesion to metals or plastics, so that it cannot be used for the manufacture of laminates such as glass/metal laminates and glass/plastic laminates.